Up to 70% of adults with bipolar disorder smoke, compared with only 20% of the general population, leading to disproportionately high rates of tobacco-related disease and mortality. Quit rates for smokers with bipolar disorder are less than half that of smokers without psychiatric disorders (17% vs. 43%). Key barriers to improving quit rates in this group are: (1) unique challenges of quitting for smokers with bipolar disorder that are not addressed in standard cessation counseling, such as the commonly held belief that smoking helps to manage symptoms of the disorder, and (2) limited access to tobacco treatment within the mental health care system. New approaches are greatly needed to address both of these barriers. Web-based Acceptance and Commitment Therapy (ACT) is a new model of smoking cessation treatment that more than doubled quit rates compared to the current standard, the US government's Smokefree.gov site (23% vs. 10% at 3-month follow- up). Adding nicotine replacement therapy (NRT)--an effective and accessible pharmacotherapy-and targeting this intervention to address the major barriers to quitting for smokers with bipolar disorder could significantly improve the extremely low quit rates. The proposed project involves development and pilot testing of a targeted, web-based ACT intervention for smokers with bipolar disorder (WebQuit Plus), which builds on our promising pilot data showing 40% quit rate and 90% acceptability for this intervention when delivered as face- to-face, individual therapy. The study will be conducted in two phases. The first phase will consist of intervention development and web site usability testing (n=12). The second phase will be a pilot randomized, controlled trial at three sites within the National Network of Depression Centers (NNDC), comparing WebQuit Plus (n=30) to Smokefree.gov (n=30). Both interventions will be delivered in combination with the nicotine patch. A primary aim of the study is to determine feasible procedures for conducting a larger, multi-site efficacy trial within the NNDC, with primary feasibility outcomes including: (1) recruitment (i.e., number approached, screened, eligible, and consented; reasons for ineligibility or refusal), (2) completion of the intervention and (3) outcom data retention. Another primary aim is to compare WebQuit Plus to Smokefree.gov on treatment satisfaction and utilization, ACT's theory-based mechanism of change smoking cessation outcomes, and bipolar disorder symptoms at the end of the 10-week treatment period and at 1-month post-treatment follow- up. This study is significant and innovative in two key respects: (1) it applies a promising new treatment (ACT) with a novel mechanism of action for smoking cessation (i.e., acceptance) to the problem of low quit rates among smokers with bipolar disorder, and (2) the intervention is web-based, making it accessible, potentially cost-effective, and easily disseminated to mental healthcare settings. If found to be effective in the larger trial that would be informed by this pilot trial, WebQuit Plus could have an enduring, positive impact on the high prevalence of smoking-and smoking-related illnesses-among adults with bipolar disorder.